GaN is widely used in LED light sources. However, GaN has a wide band gap and therefore cannot emit light in the visible range by itself. InN has too narrow a band gap, due to which it cannot emit light in the visible range. Ga is a high-cost element, and In is a scarce element. Various zinc nitride compounds have been proposed; however, for example, ZnSnN2 is difficult to produce in the form of a p-type semiconductor, and Ca2ZnN2 is an indirect band gap semiconductor. The problem with these zinc nitride compounds is that, for example, they are unsuitable for use in light-emitting devices or high-efficiency solar cells (Non Patent Literature 1).